An extended refinery maintenance shutdown (or, “turnaround”) is typically performed every 10-20 years, and can interrupt wastewater flow to Activated Sludge Units (ASU). An ASU assists in remediating refinery wastewater by removing excess nitrogen and carbon compounds. The ASU employs a broad consortium of microorganisms to remove water-soluble pollutants that are regulated under the Clean Water Act in the Unites States, and local and national regulations in other countries. These microorganisms depend on a constant influx of wastewater to provide both a food source (residual organic carbon) as well as nutrients (mainly nitrogen and phosphorus) needed for their survival.
An extended interruption in the flow of refinery wastewater leads to the death of these microorganisms and a can result in a significant delay when restarting refinery operations due to insufficient wastewater remediation capacity within the ASU.
Accordingly, a need exists for a process and system that can prevent large-scale loss of microbial flora in the ASU during an extended maintenance periods where a constant influx of refinery wastewater is not available.